The present invention relates to a raw material of a chemical vapor deposition (hereinafter referred to as xe2x80x9cCVDxe2x80x9d) for forming an electrode or a wiring film that is employed in a dielectric memory such as Dynamic Random Access Memory (hereinafter referred to as xe2x80x9cDRAMxe2x80x9d), or ferroelectric Random Access Memory (hereinafter referred to as xe2x80x9cFeRAMxe2x80x9d), or as a dielectric filter of an electronic device, and it also relates to an electrode and a wiring film that are formed thereof.
Recently, a high integration of memory device in the semiconductor has been rapidly advancing. Progress in view of the high integration of, for instance, DRAMs resulted in a bit number that was four times larger than three years ago. This progress has been made in order to obtain an device having high speed processing, low consumption of electricity and low cost. However, a capacitor as for a component of a DRAM must have a specific capacitance, in spite of improvement in the integration of the device. Therefore, to secure the required capacitance has been investigated by various methods, for instance, decreasing the film thickness of material for capacitor, improving the permittivity by changing materials, or increasing the effective area by employing a three-dimensional shape, etc.
On the other hand, according to the high-performance of a semiconductor device and the like, it has become necessary to achieve a low resistance of an electrode or a wiring film employed therein and to achieve an affinity with the material of a capacitor or the material of a substrate. Instead of Al that has been generally employed as a material for forming an electrode in the conventional art, there have been employed Cu, Ir, Ru, Pt or, if necessary, an oxide thereof, as a material for forming an electrode and wiring.
Properties required for an electrode material are excellent electric properties of the obtained electrode, namely, small electrical resistance, and it is also important to have a required performance such as a favorable affinity with a dielectric material of a capacitor or with a material of a substrate thereon, and to be formed on a substrate of complicated shape.
For instance, in order to form an electrode as a thin film onto a capacitor of a stepped DRAM, it is necessary to have a favorable coverage of an object of complicated shape. In case of an electrode employed as a capacitor employing an oxide as a dielectric, it is necessary to prevent a decrease in property of the dielectric, and to have the favorable affinity between the dielectric and the electrode. For instance, in a capacitor of (Ba, Sr) TiO3 or Srxe2x80x94Bixe2x80x94Taxe2x80x94O, a metal of the platinum group such as Pt, Ru or Ir may be employed, and the interface between the dielectric and the electrode is preferably made of a conductive material of the oxide group such as RuO2 or IrO2.
On the other hand, since the wiring material may be required, depending on the application thereof, to have a lower electric resistance than that of a conventional material such as Al, is attractive Cu, and development has been made in the field of Cu wiring technique. Mostly, of the film forming process for the electrode is sputtering, and it has partially been considered to employ a CVD method for Cu and the like.
Under these circumstances, though it is most advantageous to form a film through the CVD method, there is currently a large problem that there are no materials which present stable and favorable evaporating properties as the CVD source material. This is mostly due to the fact that the evaporating properties of dipivaloylmethane (DPM) compounds of the xcex2-diketone group, mainly employed as the CVD material, are not favorable. This is also mentioned, for instance, in Lecture Number 9a-P- 11 of the Collection of Preparatory Drafts of the 52nd Applied Physics Academy Science Meeting, and is considered to be a problem owing to the essential instability of metallic DPM compounds. Nevertheless, the CVD method has been actively investigated, and there are also reported extreme cases in which the material is wasted after employing it once due to the above described instability of the material. In only case of Cu, materials with a relatively high vapor pressure have been developed, but they present a problem that the material contains fluorine in it or it lacks stability.
Therefore, there are no known techniques for manufacturing a film for an electrode, which has favorable performance and repeatability of manufacturing that overcome these problems owing to the above described material (raw material), and thus these materials need to be developed.
Japanese Unexamined Patent Publication No. Hei.-9-82907 discloses, as an example of the above described conventional art, a problem presented in case that the conventional metal film of Pt or the like was formed as an electrode film, namely, a decrease in permittivity and a generation of leak current according to decreasing the thickness of the capacitor film. As a method for solving this problem, it has been suggested to specify a site of Ba, Sr, Ti, and to form a (Ba, Sr) TiO3 film with a metal oxide as a main component through a sputtering method, which has a perovskite crystal structure of ABO3 type. The film contains approximately 1% by weight of Fe and has a thickness of approximately 20 nm.
Japanese Unexamined Patent Publication No. Hei. 8-288242 relates to the formation of Cu film through the CVD method, and it discloses a device in which plural supplying pipes can be sequentially employed as a measure against clogging of pipes that is apt to occur when supplying a Cu raw material. It also discloses a method in which an organic metal is dissolved in a suitable solvent as a Cu source material.
Further, Japanese Unexamined Patent Publication No. Hei. 9-27602 discloses forming of a (Ba1-X,SrX)RuO3 film through the sputtering method as an electrode in case of employing (Ba1-XSrX)TiO3 as a capacitor film, and it also refers to a CVD material containing Ru(C5H5)2 that is employed by dissolving in a solvent.
Formation of film for electrode had conventionally been performed in the above manner, and since forming of film disclosed in the Japanese Unexamined Patent Publication No. Hei. 9-82907 had been performed through the sputtering method, there were still presented problems that the film had a poor coverage property, and that forming onto a capacitor of complicated shape was difficult.
In the method disclosed in the Japanese Unexamied Patent Publication No. Hei. 8-288242, Cu was employed as the electrode film, and the stability was not yet sufficient also in the Cu organic metal compound as described herein. And low temperature decomposition is apt to occur even if it has a relatively high vapor pressure, so that the controllability at the film forming is inferior. Thus, the device and the film forming process have been devised to cope with this problem. Further, though it discloses that an organic metal compound is dissolved in a suitable solvent to obtain a Cu material, it does not refer to the effects thereof, that is, the stability or the controllability as a raw material.
Similarly, the Japanese Unexamined Patent Publication No. Hei. 9-27602 does not refer to a stable supply of the organic metal material.
As described so far, it was difficult to supply the CVD material to a CVD reaction portion stably (to perform a stable supply) through heating at a low temperature owing to the stability and the evaporating deficiency of the CVD material for forming an electrode film through the conventional CVD method. Thus, there was a large problem that an electrode film of desired material having favorable properties could not be formed stably. Further, in case of heating at a high temperature in order to improve the evaporating efficiency of the CVD material, the raw material was transported while undergoing pyrolysis, and the deficiency in film shape and the lag of film thickness with the pre-determined value could not be avoided.
Also, a conventional method presented problems that the film formation speed could not be stabilized in case the evaporating speed was suppressed and the synthesis (reaction) time was prolonged, since the stability of the material sequentially degraded and the evaporating property gradually decreased. Further, it was impossible to avoid an increase in resistance in case of forming a complex conductive oxide film, since the composition in the film thickness direction became irregular. Therefore, there has been strongly desired a CVD source material which presents a stable evaporation even after a multiple or a long-term use and a favorable evaporating property even at a low temperature, as the CVD source material containing the desired metal for forming various required electrode films. But no materials are available that sufficiently satisfy the above requirements, while various raw materials are presently suggested.
The present invention has been made for solving the above problems of the conventional material that had been employed in the conventional CVD method so far, and the present invention has made it possible to stably transport (supply) the material for forming an electrode of platinum group metals, Cu or an oxide thereof to a reaction portion, and to form an electrode thin film of favorable performance at high repeatability owing to the stable transportation. It has also made it possible to improve the coverage property to an object of complicated shape.
The electrode film formed by the present invention is applicable to not only semiconductor but also wiring of other electric devices.
According to one aspect of the present invention, there is provided a CVD material for forming an electrode, in which at least one organic metal compound, of which metal is a platinum group metal or Cu, is dissolved in tetrahydrofuran.
Another aspect of the present invention, there is provided a CVD material for forming an electrode, in which at least one organic metal compound, of which metal is a platinum group metal or Cu, is dissolved in a solvent containing tetrahydrofuran.
Preferably, the amount of moisture is not more than 200 ppm.
Preferably, the organic metal compound is an complex organic metal compound containing plural metal elements, and that the metal elements of the organic metal complex compound are at least one metals selected from the group consisting of Ru, Pt, Ir, Pd, Os, Rh, Re and Cu.
Preferably, the organic metal compound is a compound in which a metal atom is combined with an organic group through an oxygen atom.
Preferably, the compound in which the metal atom has combined with the organic group through the oxygen atom is acetylacetonato, dipivaloylmethanato, alkoxide, hexafluoroacetylacetonato, pentafluoropropanoylpivaloylmethanato or a derivative thereof of any one of the metal selected from the group consisting of Ru, Pt, Ir, Pd, Os, Rh, Re and Cu.
Preferably, the compound in which the metal atom has combined with the organic group through the oxygen atom is a dipivaloylmethanato group compound of the metals selected from the group consisting any one of Ru, Pt, Ir and Cu.
Preferably, the organic metal compound is cyclopentadienyl or a derivative thereof of any of the metals selected from the group consisting of Ru, Pt, Ir, Pd, Os, Rh, Re and Cu.
Another aspect of the present invention, there is provided an electrode for a capacitor which is formed with the CVD material for forming an electrode through the CVD method.
Another aspect of the present invention, there is provided a wiring film which is formed with the CVD material for forming an electrode through the CVD method.
The inventors have achieved the present invention through detailed considerations by evaluating evaporating properties of solid type DPM compounds mostly employed in the conventional CVD method, and further evaluating properties of electrode film formed by employing the mentioned material and the process at forming.